<p>U disertaciji su prikazana istraživanja vezana za objektivnu i subjektivnu,<br />psihofizičku metodu koja u eksperimentu utvrđuje koliki uticaj imaju različiti<br />parametri rasterizacije kao i dimenzija posmatrane slike na percepciju<br />realističnog prikaza i zrnaste strukture uz poređenje sa objektivnim metodama<br />obuhvaćenim eksperimentalnim merenjima. U metodologiji istraživanja su<br />korišćeni uzorci rastrirani sa dva različita tipa rastera frekventno<br />modularni i amplitudno modularni. Poznatim i priznatim naučnim metodima<br />obrade podataka došlo se do relevantnih rezultata koji potvrđuju različitost<br />posmatranih reprodukcija i model kontrole parametara rasterizacije.</p> / <p>The research presented in this dissertation is related to the image reproduction quality<br />assessment. Dissertation was designed to determine the impact of halftone attributes<br />on image quality. Objective and subjective quality assessment results were designed<br />to complement recently published findings for quality assessment. These attributes are<br />directly dependent on the chosen halftoning method. In this research the samples were<br />halftoned using two different types of screening methods: frequency modulated and<br />amplitude modulated method. Experiment data samples, were analysed by adequate<br />statistical methods. Results indicate significant influence of halftoning method on the<br />quality assessment and defines control model.</p>

<p>A halftoning method with Neugebauer Primary Area Coverage direct binary search (NPAC-DBS) is developed. With the optimized human visual system (HVS) model, we are able obtain homogeneous and smooth halftone colored image. The halftoning is based on separating the colored image represented in Neugebauer Primary in three channels based on human visual system, with swap-only DBS, we arrange the dots to bring the error metric to its minimum and the optimized halftone image is obtained. The separation of chrominance HVS filters between red-green and blue-yellow channels allows us to represent HVS more accurately. Color halftone images generated using this method and method of using traditional screening methods are compared.</p> <p>In order to speed up the halftone process with similar quality of NPAC-DBS, we developed PARAWACS screens for color halftoning. PARAWACS screen is designed level by level using DBS. With PARAWACS screen, we can create halftone using simple pixel by pixel comparison with the merit of DBS. We further optimized the screen to achieve the best quality.</p> <p>Next, a novel halftoning method that we call Ink-Saving, Single-Frequency, Single-Angle, Multi-Drop (IS-SF-SA-MD) halftoning is introduced. The application target for our algorithm is high-volume production ink-jet printing in which the user will value a reduction in ink usage. Unlike commercial offset printing in which four-colorant printing is achieved by rotating a single screen to four different angles, our method uses a single frequency screen at a single angle, and it depends on accurate registration between colorant planes to minimize dot-overlap especially between the black (K) colorant and the other colorants (C, M, and Y). To increase the number of gray levels for each colorant, we exploit the multidrop capabilities of the target writing system. We also use the hybrid screening method to yield improved halftone texture in the highlights and shadows. The proposed method can help preserve ink significantly.</p>

<p>Beacon AB has been producing Gobos for some time. A Gobo is a small round sheet used in projectors almost like a slide. It is used mostly in the commercial and entertainment business. Today these Gobos are created by using a film (also called mask). A digital exposure machine called LIOS has been developed to make it possible to create Gobos using direct exposure. This means a film will no longer be necessary and it will also make the process faster and cheaper. </p><p>To be able to use LIOS in the industry a lot of work still has to be done. An image is sent to the display in LIOS. This image comes from a computer connected to LIOS and at the end of the process it will be reproduced on the Gobo. This image can be modified before it is sent to LIOS so that a better result can be achieved in the end. The problem is that once the process is complete the image will be binary, which means halftoning is going to be used. The goal of the research described in this paper is first to test the properties of LIOS, second to create a halftoning method especially designed for those properties. </p><p>The resultof this thesis is an AM (Amplitude Modulated) method that uses a modified threshold matrix. Using this method would not give a satisfying result unless some of the distortions could be corrected somehow. This can however be done using a property available for the display in LIOS. The display can handle grayscales but since etching is used later in the process the final result will be a binary image (only black and white). This means that even though the image will be binary in the end, these grayscales can still be used to improve the result. The equipment that was available when this thesis was done was not fully developed why the grayscales are used to correct distortions. </p><p>The resulting method will most likely be good enough to produce Gobos with a satisfying quality. The method has never been used before and it introduces a new way of making corrections for halftoning. There are still some practical problems left to solve before LIOS can be used to reliably produce Gobos. Using better equipment can solve several of these problems but not all of them.</p>

<p>Halftoning methods can be divided into two main categories, namely AM (Amplitude Modulated) and FM (Frequency Modulated). Some printing methods, such as Flexography, are not able to produce dots small enough to handle the highlights and the shadows of the original image by just using AM halftoning method. To overcome this problem FM method is used in the highlights (and the shadows) and an AM method in rest of the image.</p><p>Hybrid halftoning (combination of AM and FM) technique for grayscale images has already be presented showing the best way to place FM and AM dots in the resulting binary image. This thesis work is and extension of that and presents hybrid technique for color images. In color images, besides the problem of transition area between AM and FM, a number of other factors needs to be addressed. One of such factors is to define the starting point of FM technique in different color channels. In this work all the possibilities of combining AM and FM in different color channels have been investigated and then the best approach for hybrid color halftoning is proposed. This approach not only uses the best solution for starting point of FM halftoning in each channel but also places the different color dots in the highlights, as homogenously as possible.</p>

Halftoning methods can be divided into two main categories, namely AM (Amplitude Modulated) and FM (Frequency Modulated). Some printing methods, such as Flexography, are not able to produce dots small enough to handle the highlights and the shadows of the original image by just using AM halftoning method. To overcome this problem FM method is used in the highlights (and the shadows) and an AM method in rest of the image. Hybrid halftoning (combination of AM and FM) technique for grayscale images has already be presented showing the best way to place FM and AM dots in the resulting binary image. This thesis work is and extension of that and presents hybrid technique for color images. In color images, besides the problem of transition area between AM and FM, a number of other factors needs to be addressed. One of such factors is to define the starting point of FM technique in different color channels. In this work all the possibilities of combining AM and FM in different color channels have been investigated and then the best approach for hybrid color halftoning is proposed. This approach not only uses the best solution for starting point of FM halftoning in each channel but also places the different color dots in the highlights, as homogenously as possible.

Beacon AB has been producing Gobos for some time. A Gobo is a small round sheet used in projectors almost like a slide. It is used mostly in the commercial and entertainment business. Today these Gobos are created by using a film (also called mask). A digital exposure machine called LIOS has been developed to make it possible to create Gobos using direct exposure. This means a film will no longer be necessary and it will also make the process faster and cheaper. To be able to use LIOS in the industry a lot of work still has to be done. An image is sent to the display in LIOS. This image comes from a computer connected to LIOS and at the end of the process it will be reproduced on the Gobo. This image can be modified before it is sent to LIOS so that a better result can be achieved in the end. The problem is that once the process is complete the image will be binary, which means halftoning is going to be used. The goal of the research described in this paper is first to test the properties of LIOS, second to create a halftoning method especially designed for those properties. The resultof this thesis is an AM (Amplitude Modulated) method that uses a modified threshold matrix. Using this method would not give a satisfying result unless some of the distortions could be corrected somehow. This can however be done using a property available for the display in LIOS. The display can handle grayscales but since etching is used later in the process the final result will be a binary image (only black and white). This means that even though the image will be binary in the end, these grayscales can still be used to improve the result. The equipment that was available when this thesis was done was not fully developed why the grayscales are used to correct distortions. The resulting method will most likely be good enough to produce Gobos with a satisfying quality. The method has never been used before and it introduces a new way of making corrections for halftoning. There are still some practical problems left to solve before LIOS can be used to reliably produce Gobos. Using better equipment can solve several of these problems but not all of them.

<p>In the first chapter, we illustrate a big picture of the printing systems and the concentration of this dissertation. </p><p><br></p><p>In the second chapter, we present a tone-dependent fast error diffusion algorithm for color images, in which the quantizer is based on a simulated linearized printer space and the filter weight function depends on the ratio of the luminance of the current pixel to the maximum luminance value. The pixels are processed according to a serpentine scan instead of the classic raster scan. We compare the results of our algorithm to those achieved using</p> <p>the fixed Floyd-Steinberg weights and processing the image according to a raster scan ordering. In the third chapter, we first design a defect generator to generate the synthetic abnormal</p> <p>printer sounds, and then develop or explore three features for sound-based anomaly detection. In the fourth chapter, we explore six classifiers as our anomaly detection models, and explore or develop six augmentation methods to see whether or not an augmented dataset can improve the model performance. In the fifth chapter, we illustrate the data arrangement and the evaluation methods. Finally, we show the evaluation results based on</p> <p>different inputs, different features, and different classifiers.</p> <p><br></p><p>In the last chapter, we summarize the contributions of this dissertation.</p>

<div> <div> <div> <p>Periodic clustered-dot halftones are widely used in electrophotographic printers due to the relatively poor print stability of this class of printers. It is important to analyze the nature and the causes of perceived fluctuation in order to understand the factors that prevent the high-end digital presses from achieving the same print quality as the commercial offset presses. In order to better approximate the screen sets used for the commercial offset presses, irregular screen sets can be considered. We start by developing a set of candidate screen tile-vectors that best fit the specified screen frequency, screen angle, and printer resolution. We then perform Fourier-based analysis of regular and irregular periodic, clustered-dot halftone textures in order to understand how perceived fluctuation relates to the halftoning technology. After exploring the search for the best single separation geometry, we consider the superposition of multiple periodic clustered-dot halftones, and propose to apply HVS-based model, which assists us in finding the best color assignments to the superimposed halftones. It turned out that the choice of the best color assignments depends on different combinations of colorant absorptance values, hence we propose to apply different color assignments within the image depending on the local color and content of the image. Next, we propose a step-by-step screen design for standard and high resolution periodic irregular clustered-dot halftones. Finally, we presented monochrome DBS-based screen design with overlapping clusters of 2 × 2 or 3 × 3 pixels, which can also be used in electrophotographic printers. </p> </div> </div> </div>

<p>This study is a thesis for the Master of Science degree in Media Technology and Engineering at the Department of Science and Technology, Linkoping University. It was accomplished from November 2002 to May 2003. </p><p>Objective image quality measures play an important role in various image processing applications. In this paper quality measures applied on halftoned images are aimed to be in focus. Digital halftoning is the process of generating a pattern of binary pixels that create the illusion of a continuous- tone image. Algorithms built on this technique produce results of very different quality and characteristics. To evaluate and improve their performance, it is important to have robust and reliable image quality measures. This literature survey is to give a general description in digital halftoning and halftone image quality methods.</p>

This study is a thesis for the Master of Science degree in Media Technology and Engineering at the Department of Science and Technology, Linkoping University. It was accomplished from November 2002 to May 2003. Objective image quality measures play an important role in various image processing applications. In this paper quality measures applied on halftoned images are aimed to be in focus. Digital halftoning is the process of generating a pattern of binary pixels that create the illusion of a continuous- tone image. Algorithms built on this technique produce results of very different quality and characteristics. To evaluate and improve their performance, it is important to have robust and reliable image quality measures. This literature survey is to give a general description in digital halftoning and halftone image quality methods.